System of control for electrically operated lifts



A. A. cHuiaB May 17, 1938.

SYSTEM OF CONTROL FOR ELECTRICALLY OPERATED LIFTS 4 Shets-Sheet 1 FiledApril 24; 1936 Fig. I.

A. A. CHUBB May 17, 1938.

SYSTEM OF CONTROL FOR ELECTRICALLY OPERATED LIFTS Filed April 24, 1936 4Sheets-Sheet 2 y 1 1938. A. A. CHUBB 7 2,117,839

SYSTEM OF CONTROL FOR ELECTR ICALLY OPERATED LIFTS Filed April 24, 19364 Sheets-Sheet 4 M N R T U V 9 J 4 TL v R t2 4 3 3 L t1 mm/vm? amwuafuPatented May 17, 1938 I UNITED STATE PATENT OFFIQ'ZE SYSTEM OF fiONTROLFOR ELECTRICALIJI OPERATED LIFTS Alexander Albert Ghubb, Coventry,England, assignor to The General Electric ompany Lim ited, London,England Application April 2d, 1936, Serial No. 76,115 In Great BritainMay 1, 1935 9 Claims. (Cl. WE -452} My invention relates to systems ofcontrol for the latter operates a relay which first inserts electricallyoperated lifts, and has for its object the rotor circuit by means ofslip rings a value the pro-vision of means whereby a lift may be ofresistance determined by the position of the brought to rest accuratelyat a floor, and irzdeload measuring wiper switch. The relay thuspendently of the load carried by it. operated then reverses theconnections to two The load in a lift may vary considerabl of the phaseleads to if on approaching a floor at which it is required lift motor toact as to stop, a brake having a constant retarding effect is applied,then if the load is such as 10 help the motor driving the lift, the liftwill c shoot the fiocr level. Conversely, if the load hinders thedriving means, the lift will cease to required floor indepe 21g acceleithe lift is brought i rest substa c ntly of the of known type movebefore it reaches the required floor. whereon a holding It is, ofcourse, lrnown to provide means whereplied and the lift he at therequired floor. by this effect may be avoided. The means usu- Theinvention may of course. be applied to ally include some method ofweighing the actual lift driven by a D. C. motor in which case operaload in the lift, and then using this result to tion. of the inductorrelay causes reversal the control the speed of the lift driving motoreither armature connections and the ihsc tion te during acceleration ordeceleration or both. armature circuit of a resistance 1 .ng a valueThis method is applicable only to lifts in which proportional to theload carried. by the lift at 2C control of the motor speed is by meansof a that instant.

variable voltage applied to the armature of the Reference should. now bemade to the accom driving motor, such systems of control being panyingdrawings Figures 1 and 1d of which show relatively expensive. anembodiment of my invention, and Figure 2 According to my invention, in asystem of conis a modification providing graduated braking. 25

trol for an electrically operated lift, means. are Figure 1 is a sc-called divorced contact draw provided whereby the load in the lift ismeasing and to assist in understanding it reference ured duringacceleration after starting from rest, should be had to Figures 3 and 3awhich are a whereafter the lift is brought to restat a required codesheet for the Figures 1 and la.

position by causing the driving motor during ac- Referring to Figure 1,it will be seen that as 30 celeration to be energized in a reversedirection, illustrated the lift driving motor is an induction the extentof such energization being determined motor which consists of a rotor R0fixed to a by the load measuring device. shaft SH and the latter carriesother devices -In an embodiment of my invention, a current referred tolater. The rotor R0 is driven by which ls'proportional both to thesteady voltage the stator windings ST connected through suit- 35 acrossone phase of a 3-phase supply to an inable switching devices (contactsa1, 1L2, d1, dz) ductor motor and also to the current in one to athree-phase supply as shown. The rotor Phase of the Said pp y, flOWSthrough a reslstcurrents are preferably controlled by means of ancecontrolling current to a lift load relay. ta ed resistances SA, SB andSC, the values 40 When the lift starts from rest, a step-by-step ofthese resistances being determined by the 46 Wiper Sw c av g a contactbank connected associated switch banks G3, G4, G5 and the coopto tapp gs0 he load relay resistance comcrating wipers, and by the relay contacts(b1, b2, mences to move its wipers over this contact bank, b connectedthereto as explained later.

T load lay being connected in circuit with When the lift is stationary,a holding brake K the w p m v over the resistance rvings isde-energlzed, and clamps the lift driving shaft 45 is slowly energizedas the resistance is decreased solidly. When current is supplied to themotor and whe e Current through the d rel y and during movement of thelift away from the reaches a particular value the relay operates floorthis holding brake is energized and by Opand through its contact opensthe switch stepcrating releases the driving shaft allowing the 50 ping Crcu and Stops the Switch from t pping. carriage L0 to move in the liftwell. During 50 Nothing further happens until the lift is redecelerationof the motor the speed of the carquired' to stop and then only aftercutting out riage is reduced by reversing the stator c0nnecmanualcontrol and, when an inductor plate is tlons (1n, 11.2, (11, d2) so asto reverse the direcpassed at some distance prior to the required tionof the current, and then the carriage is 5 floor. When the lift passesthis inductor plate finally brought to a standstill by release of theholding brake K when the motor circuit is out as the lift reaches thefloor. A typical traverse of the lift will now he described so that theoperation of the system may be made manifest.

Assuming that the lift is at the bottom or" the shaft and it is requiredto travel to an upper floor, the manual control up lrey SU is closed.This key is manually operated, and is held closed until some distanceoeiore the required door is reached. The up key SU is mechanicallyinterlocked With the corresponding down control key closure of whichcauses the liitto travel downwards, so that only one key can be operatedat a time.

Closure of the up SU causes a control relay B and the up relay U tooperate. Their con" tacts perform the following functions:*

for, be and In moving to their upper positions adjust the values ofresistances SA, SB SC for starting the driving motor.

or by closing loclzs relay I5 operated to the contact or" the floorrelay 1 (see later).

in closing prepares an operating path for a re-- sistance relay R and aswitch starting relay V.

to and in close circuits for the stator windings ST so as to operatethernotor to drive the lift in an upward direction.

its closing loclrs up relay U operated to the contact of stop relay S(see later).

it; by opening prevents false operation of clown relay D.

as closing prepares a locking circuit for load relay as opening cream aself-interrupting circuit for switch stepping magnet GA, used later forrestoring the wipers.

1L7 closing prepares to operate reversing relay M later.

to closing operates a two position relay N to position suitable fordeceleration (see later). This relay is of the two=position type, itscontact an remaining in the position to which it was last moved untilenergized to a fresh position.

Two actions now take place simultaneously. Large currents flow in therotor windings (if the lift load is an opposing one) these currentspassing through (by way of contacts e1, a, bi) the starting resistancesthe lower sections of) SA, SB and SC, and being limited by them. Inaddition, in view of circuit connections acrosstwo phases of the rotorcircuit a potential appears across the primary of the rotor circuittransformer Q, this potential being rectified by the rectifier RC andthereafter operating an initiating relay T via a resistance shortcircuiting contact or.

1 closing operates switch starting relay V to positive on be now closed.7

in by opening prevents operation of resistance relay B when contact v3closes.

v1 opening removes the short circuit across the resistance RD therebyreducing the current through relay T, though this. initiating relay doesnot release at the moment.

v2 closes a holding circuit which locks switch starting relay Voperated.

v4 closes a self-interrupting cucuit of the.

tential) and is derived from two of the phase leads through the phasecorrecting condenser PH. The other current in the primary isproportional to the current flowing through the resistance BE, in thestator circuit, this current accordingly being proportional to this loadin the lift. it this load is a heavy opposing one, a large startingcurrent flows through the resistance RE, the resulting constantpotential current flowing in the second half of the primary of the transformer I? being in phase with and therefore helping the current flowingin the first half of the primary. If on the other hand, the load in thelift is a helping one, the starting current through the resistance maybe small or even negative,

Ii. c. it may he 183 displaced f one the phase of the current in thefirst half of the primary. Whatever the starting current, a potentialpronortional thereto is induced in the secondary of the transformer thispotential ceing rectified by the rectifier RB, and applied vie. liewiper of the switch contact haul: Gt through the tapped resistance toone coil of the load relay As will be remembered, the wiper along withthe other switch wipers is being stepped by the stepping magnet GA overthe contacts associated with it, these contacts being connected in suchfashion to the tapped resistance RG as rapidly to reduce the value ofthe resistance in series with the load relay E. This permits an increaseof the current passing through the coil of the load relay until itoperates, the point at which such operation takes place being determinedby the potential derived from the secondary of the transformer 'P, andhence from the current in the stator leads, this current beingdetermined by the load in the lift. When the load relay operates, itscontact e1 closes a holding circuit which locks the relay operated tocontact its, and contact e-i opens the self-interrupting circuit oistepping magnet GA so that the wipers of the switch cease to step. itmay therefore ice-said that the wipers of the stepping switch GA havenow been posltloned at a point corresponding to the load in the lift.

Reverting now to the rotor circuit, when the potential derived fromtransformer Q falls, after the initial heavy current flow at starting tosuch a value that the current through the resistance RD and relay T isinsufilcient to maintain the latter operated, relay '1 releases, and itscontact by closing operates resistance relay R, in being closed. Thecontacts n and T2 of resistance relay it short circuit resistances SA,SB and SC, and the rotor runs up to full speed, driving the lift in theshaft.

Nothing further happens until the lift reaches a point some distanceahead of the floor at which stopping is required. The manual control keySU is then opened. At 'a predetermined distance ahead of each floor, twoinductor plates (not shown) are provided in the shaft of the lift, theseplates co-operatlngrespectively with the inductor relays floor relay Yand stop relay S. When the lift, in approaching the floor at which it isto stop, passes one of the said inductor plates floor relay Y is firstmomentarily operated, opening its contact. Since relay B can now nolonger be held operated in series with up relay U, (SU being open), itis released by the opening of the contact of the floor relay U, thecontact 174 of control relay B, now open, preventing re-operation whenthe inductor floor relay contacts reclose.

bi, b: and b3- dropping to the lower contacts'prepare circuits throughthe resistances SA, SB and SC of values such that the currents permittedby them to flow in the rotor circuit are commensurable. with the load inthe lift, i. e. if the load is 1 tact releasing the up relay U. Thereversing relay M does not release at the moment, for as indicated it isslugged.

141 and uz opening de-energize the motor stator ST. The brake K is notre-applied at this point as it is given a slight time lag.

u: opening cuts the holding circuit and prevents re-operation of the uprelay U.

m closing prepares an operating path for operation of down relay D.

U opens the circuit of load relay E, which being slugged, does not yetrelease.

it! opens the circuit of reversing relay M, but this relay, beingslugged, does not yet release.

When stop relay S releases after passing its inductor plate and beforereaching the floor, its

contact by closing now operates down relay D via be, 1m, m and U4.

di and d2 now close the stator circuits in a direction the reverse ofthat previously employed for driving the lift.

(is closed holds load relay E operated.

. d1 closed holds reversing relay M operated.

The lift now commences to slow down, its rate of deceleration beinggoverned by the setting of the wipers G3, G4 and G5, this setting being,as previously described, controlled by the lift load.

When the lift reaches the desired floor, the inductor stop relay S isagain operated from a further plate at the floor (not. shown) in theshaft, and the opening of its contact releases down relay D andreversing M.

di and (is opening break the circuits of the stator ST, therebydeenergizing the motor and the holding brake magnet K. This brake, inreleasing, clamps the motor shaft and stops the carriage.

d5 releases load relay E.

d6 and m: by closing restore a self-interrupting path for the switchstepping magnet GA via the interrupter contactg and bank G2. The switchnow steps by self-interruption to the first contact I and there stops.

All apparatus is now restored to a normal-deenergized condition and isready for a further traverse.

From the foregoing, it will be seen that the lift is run into a floorunder the combined effect of two forces. These are due to the load inthe lift and the currents flowing in the rotor circuit.

Since the latter is varied automatically in opposition to the formerafter each time the lift starts from rest, accurate levelling under allconditions is ensured.

Figure 2 shows a modification whereby a more gradual deceleration may beobtained. The stepping switch GA with its several wipers is now providedwith another stepping magnet GB, but this stepping magnet is adapted todrive the wipers G1 to G6 (G0 being added) in the direction oppositefrom that indicated by the arrows which indicate the stepping directionsby stepping magnet GA. In addition, the further bank G6 is required, andthree cycle relays AX, BX and CX. The action of this addition is asfollows.

During the initial setting of the wipers of the switch by load relay E,the load relay E is now adi'usted to operate after the wipers of theswitch have moved rather farther than that previously described forFigure 1. Then when relay M operates as previously described at thecommencement of the decelerational period, one of the cycle relays AX,BX or CX is operated by contact 1113. If relay AX operates, then as:opening de-energizes relay BX.

an closing energizes the stepping magnet GB via bank G6.

brr closed operates relay CX.

0x1 opening releases relay AX.

(ll'l closing operates relay BX.

are opening de-energizes stepping magnet GB, and the wipers of theswitch take a ste" backwards.

ban opening releases relay CX.

can closing operates relay AX.

This cycle continues, the backward stepping of l the Wipers of theswitch causing resistance to be cut out of the rotor circuit to thusgradually increase the braking effect on the lift.

When the latter is brought to rest at a floor, release of reversingrelay M causes interruption of backward stepping, the wipers of theswitch being restored to a normal position in the manner previouslydescribed.

Although a manually started lift has been described, it should beunderstood that the invention may easily be applied to an automaticallystarted or stopped lift such as one operating on the so-called collectorprinciple, the only differences being those necessary to replace thehand-operated control keys SU and SD by call storage and floor selectingrelays and/ or switches of known type.

Finally, although it has been stated that the switch G varies the rotorresistances SA, SB and SC directly through its'contact banks, such aproceeding may not be advisable in the case of a lift taking largecurrents, in which case the switch wipers operate contactors of knowntype which perform the necessary resistance adjustment. Circuitmodifications of this nature, being obvious to those skilled in the art,are omitted for purposes of clarity, though I wish it to be understoodthat the scope of my invention covers all such obvious adaptations notrequiring the exercise of invention.

I claim:-

1. A system of lift control comprising a lift motor having stator androtor coils, a source of current, circuits including up and downcontacts for energizing the stator coils from said current source,starting resistances to be inserted in th circuits of the rotor coilsduring acceleration, deceleration resistances to be inserted in thecircuits of the rotor coils during deceleration of the lift, tappings onsaid deceleration resistances cooperating with wipers of a step-by-stepswitch for adjusting the deceleration resistances according to the loadin the lift, a stepping magnet for operating the wipers of said switch,a starting relay, starting relay contacts in the circuits of the rotorcoils which when the starting relay is deenergized connect saiddeceleration resistances in the circuits of the rotor coils and whensaid relay is energized connect said starting resistances in saidcircuits of the rotor coils, up and down relays for operatingtherespective stator circuit contacts, up and down lift operatingcontactors for energizing the respective up and down relays one at atime and simultaneously energizing said starting relay, and relays andcircuits controlled by the lift which, after the release of an operateddown relays for reversing the direction of the current in the statorcoils so as to utilize the braking effect of the motor according to theload in the lift in stopping the lift at a floor.

2. A system of lift control as in claim 1 wherein a relay operated bycurrent derived from the circuits of the rotor coils is adapted toinitiate operation of said stepping magnet for stepping the wipers ofsaid switch during acceleration of the lift for adjusting thedeceleration resistances according to the load in the lift to beinserted later in the circuits of the rotor coils when stoping the liftat a floor.

3. A system of lift control as in claim 1 wherein means controlled bythe current derived from the circuits of the rotor coils after startingand during acceleration of the lift motor are provided for startingoperation of the stepping magnet for stepping of the wipers of saidswitch for adjusting said deceleration resistances and a relay ar-'ranged to be operated by current derived from the circuits of the statorcoils is provided for stopping operation of the stepping magnet when thewipers thereof have been stepped an amount determined by the load in thelift.

' 4. A system of lift control asin claim 1 wherein a relay-adapted to beoperated upon release of it one of the up and down relays which has beenoperated is provided for operating the other up and down relay, that is,the down or uprelay which will reverse the current in the stator coils.

5. A system of lift control asin' claim 1 whereauasao in a relay foroperating a two position contact is arranged to be operated uponoperation of one of the up and down-relays to move said two positioncontact into position to effect operation of the other of said up anddown relays during deceleration of the lift motor.

6, A system of lift control as in claim 1 wherein a relay arranged to beoperated upon energization of the rotor coils is provided for startingthe stepping of said switch wipers by the stepping magnet and anotherrelay deriving current from the stator coils is adapted to stop thestepping of the wipers, the current for operating the last named relaysbeing controlled according to the load in the lift by one of the wipersof said switch cooperating with the tappings of a resistance arranged tobe inserted in said last named relay circuit.

7. A system of lift control as in claim 1 wherein an induction relayadapted to be operated as the lift arrives at or passes an inductorplate after an operated operating contactor has been released, isprovided for deenergizing said starting .relay so as to connect theadjusted deceleration resist ances in the circuits of said rotor coils.

8. A system of lift control as in claim 1 wherein an induction relayadapted to be operated as the lift arrives at or passm an inductor plateafter an operated operating contactor has been released, is provided fordeenergizing an operated up or down relay and energizes the other relay,that is, the down or up relay that will reverse the current in thestator coils.

9. A system of lift control as in claim 1 wherein a second steppingmagnet is provided for stepping the wipers of said switch counter to thedirection of stepping by said first named stepping magnet and a cycle ofrelays and circuits is provided for operating said second steppingmagnet for counter adjustment "of the deceleration of the decelerationresistances during deceleration of the motor.

ALEXANDER ALBERTVCHUBB.

